The Bolly GRE propellers are especially suited to the large engine use. The extra strength make them much more economical than wood (at any price), and much safer than nylon types which are prone to stretching to destruction at these sizes. The extra weight of a composite prop (compared to wood) often helps the idle characteristics of an engine.

Our first large prop was a 20 x 10 in 1979 when even wooden 20 x 10 were rare.

For large models, props size is often determined by noise, ie, on some flying fields a 18 x 10 may be regarded as too large on a ST 3000, in other areas a 19 x 10 may be regarded as too small. The choice is yours. As a rule the 3 and 4 bladed props make a good choice for noise reduction.

Avoid using tip speeds in excess of 400 MPH if noise is of concern, although 450 MPH tip speed is common in areas of low noise sensitivity.

400MPH tip speed @ 22" = 6 100 max. RPM

20" = 6 800 max. RPM

18" = 7 500 max. RPM

The range is expanding. It is easiest to list the propellers and the engines commonly used. It is our aim to manufacture prop sizes 18" to 30"in diameter, at a pitch of 10, 12 and 14" before mid1997. At the time of printing this book, we can only list many of these newer sizes as NYA.

Please remember, large slow flying models (i.e. Piper Cub, etc) will need more diameter and less pitch.

Selecting the correct propeller is a little like selecting the correct gear ratio for motor vehicles. For slow flying ,high drag models (i.e. a Piper Cub)select a higher diameter / lower pitch prop for it’s ‘pulling’ ability. The reverse is true for faster type models (ie, Laser, etc), use a smaller diameter / higher pitch propeller.

The most common mistake with 4-stroke (cycle) engines is to under-prop them, especially under pitched. It must be noted that 4-stroke engines rev slower than 2-strokes, hence when used in a similar model the 4-strokes must use a high pitch prop to fly at the same speed.

Higher pitch props. Although lacking in initial acceleration usually deliver a much smoother style of flying for reduced noise levels.

Below is a suggested prop size for the OS range of engines. Other brands (Saito, Enya etc.) will be similar.

FS 120 Supercharged 16.5 x 12.5, 15.5 x 10, 15 x 11, 14 x 10 3B, 14 x 10 4B

FS 120 Surpass 15.5 x 10, 15.5 x 8, 14.5 x 12.5, 14 x 10 3B, 14 x 10 4B

Old FS 120 15.5 x 8, 15 x 7, 13.75 x 10, 12 x 10 3B, 12.5 x 11.5 3B

FS 91 Surpass 14 x 8, 13.75 x 10, 13.25 x 10, 12 x 10 3B

FS 90 14 x 8, 13.25 x 10, 13 x 7, 12.5 x 8 3B

FS 70 Surpass 14 x 6, 13 x 7, 12 x 8, 12.5 x 8 3B,

The list is not complete, as it does not list many of the alternative 2-blade pattern, 3 or 4 blade choices.

We have done intensive testing to develop a range of propellers which will outperform any other popular pattern prop that we know of. Without doubt our GRE or CRE propellers are much safer and longer lasting than products made of wood or injection moulded plastics.

To avoid confusion we have deleted, or re designated many of the older sizes from our list. The listings below include details of the appropriate Bolly pipe to be using.

As this book is being prepared, the new .120 .140 engines are coming into use. So far we have used over 60 litres of fuel testing propellers, pipes and models for this new wave of engines. It is too early to give definite performance figures, as the engines / props and pipes are still in a development stage.

To keep noise levels down due to tip speed, we will soon have a range of 3 & 4 blade props in production. As a rule a 14.5" prop (2B) is adequate for performance, but many of these engines can easily turn a 17 or 18" prop, but the noise is too high.

4B Props = 15 x 14 4B 14.5 x 10 4B

3B Props = 16.5 x 12 3B 15.5 x 13 3B 15 x 14 3B

2B Props = 17.5 x 12 16.5 x 14.5 16.5 x 12 16 x 14 15.5 x 12.5

Below are our latest and greatest. Designed for Hanno or YS LS set-ups...

12.5 x 11 10,600 on EQ60 11,000 on EQ63 @ 490mm with OS RF etc

12.5 x 10.5W 10,400 on EQ60 10,800 on EQ63 @ 500mm with Hanno etc

12.5 x 11W 10,300 on EQ60 10,700 on EQ63 @ 505mm with Hanno etc

12.5 x 11.5W 10,000 on EQ60 10,400 on EQ63 @ 510mm with Hanno etc

13 x 10.5 new development for the .80 engines. For .80 size engines, use the higher volume EQ62, EQ62N or even better the EQ63

The 13.25 x 10 and 13.75 x 10 are props developed for the early .120 4 strokes, now proving excellent for use on the more powerful engines, with reshaping of the tip to a more modern shape.

We have had many new developments for the 4 strokes. The new FS124 pipe and CD header system is working very well. Some of the smaller props being developed for the new .120 2 stokes also suit the later more powerful 4 strokes.

Pipes = FS122 or FS 124, coupled with the CD exhaust elbow & header.

3B & 4B Props = 14.5 x 10 4B 15.5 x 13 3B 15 x 14 3B 14 x 10 3B

2B Props = 16.5 x 12 16 x 14 15.5 x 12.5 15 x 11

The older design props for earlier 4 stokes, such as 14 x 13 3B, 14.5 x 14.5, 14.5 x 13.5, 14.5 x 12.5 and 14.5 x 12W are no longer suited to modern pattern, but make excellent choices for ‘sports’ pattern.

For information updates, ask for the Bolly ‘Pattern Products’ Newsletter & price list.

Over the years pattern has changed from a high revving, conventionally muffled engines using small props to the currently used quiet pipe, low revving engine, and more recently the 120 4 stroke.

We make propellers to suit all these types of flying and C/F pipes for the piped engine and 4 strokes. We also cater for the novice pattern flyer using the .45 sized engine, piped or conventional style.

The 'narrow' and the popular "QT' style props are best suited to the short stroke engines. Popular with the ‘sports’ pattern flyer.

12 x 11 QT 10,500 on EQ60 and OS FSR etc. @ 500 mm pipe length.

12 x 12 N 10,000 on EQ60 and OS FSR etc. @ 510 mm pipe length.

12 x 11 N 10,300 on EQ60 and OS FSR etc. @ 505 mm pipe length.

12 x 10 N 10,800 on EQ60 and OS FSR etc. @ 490 mm pipe length.

10.5 x 6.5 These are in order of load on

10.5 x 8 the engine, approx 14 000 to

10.5 x 6.25 3B 12 000 depending on engine etc.

9.5 x 6.5 4B

Use the following in conjunction with a Bolly EQ45 quiet pipe at approx 47-49cm length.

10.5 x 8 These are listed in order of load

10.5 x 6.25 3B on the engine, depending on pipe, etc.

9.5 x 6.5 The expected RPM will be approx 13 500

11.25 x 8 to 11 000. Noise levels will be approx

11 x 7 4B 96 to 92 dB (less with cowled engine)

A very popular set-up uses an EQ45 @ 48cm, and an 11.25 x 8 @ 11 7000 RPM.

12 x 8

11.25 x 8 These are listed in order of load on the engine,

11 x 7.5 3B

11 x 7 4B

13.5 x 12 9 100 Early 120

14.5 x 12.5 8 500 Surpass, 120R, YS

The world's most common size of model is the .45, being used in trainers and general sports models.

Whilst a specific prop is not produced for trainers, the use of a Bolly prop will help that marginal model perform much better.

The original Bolly .45 prop was the 10 x 6. This prop will out perform any wood or nylon equivalent.

Further developments have led to the production of a 10.5 x 6.5 and 10.5 x 8. Both of these narrow blade props will offer an improvement. The 10.5 x 6.5 is better in vertical or load carrying and the 10.5 x 8 will offer top performance at lower RPM with decreased noise levels.

The 10 x 6 and 9.25 x 7 are best when wanting straight line speed - also available is the 10 x 6SP, especially designed for Australian 40 Sports Pylon. All the above props are suitable for use on .40 engines, albeit at lower RPM..

Also available, the 9.5 x 6.6 4B and 10.5 x 6.25 3B.

The Bolly Racing propellers have been developed over many years of flying and testing. An extensive range is available for almost all classes possible.

Please note: We are changing all our newer props to a number code

For FAI we have our base 8" range and the variations moulded from the base types. For models using a 2" spinner, we have found it best to use the 8" props at 7.75" diameter. And for models using a 1.5" spinner, we use the 8" props at 7.5" diameter.

8 x 6 Now out dated unless used with an older engine.

8 x 6.5N As above.

8 x 6.5 Too much load on most engines, fast if it can be made to work.

8 x 7N A very successful prop especially on OPS, best time of 1.11

8 x 7.5N Gaining favour as power levels increase, the best time of 1.13

P8 (7.7 x 6.8) A variation of the 8 x 7N.... infact a copy of the 1.11 version.

P9 (7.8 x 7.0) DeChastel designed large 1.5" hub prop. No spinner required.

P10B (7.7 x 7.2 +) NYA... Lower pitch version of P10, when less load is required.

P11 Based on the successful Harvey Westland (N.Z.) designed propeller.

Props for Australian Quarter Midget, using piped .21 engines.

7 x 5.5 Must be trimmed down in diameter to perform. Best time 1.09.

G22 (6.6 x 5.3) The 'standard' prop. Best time 1.07

G23 (6.6 x 5.6) A higher pitch G22. Best time 1.07

QM4 (6.4 x 6.6) An all new shape....best time 1.07. Best in c/f only.

QM5 NYA New single blader, with integral counter weight..

Props for Australian 1/2A, using .11 engines.

6 x 4 For lower power engines.

6 x 4.5 Alternative to the 6 x 4.

6 x 5 Popular and successful prop. Best used under 5.5" diameter.

A4 (5.6 x 5.5) An all new shape. Works well if you have the power to pull it.

A42 (5.5 x 5.0) A smaller variation of the A4, proving to be very popular.

A5 NYA New single blader with an integral counterweight.

Props for Australian Sports 45 pylon, the rules vary around the country, in some states it is compulsory to run a commercial 10 x 6 unmodified.

10 x 6SP (sport pylon) enjoys a very good reputation for performance. This prop is supplied ready to 'bolt on' in order to meet the rules.

9.25 x 7 often cut down to smaller diameters. Best in c/f only.

GENERAL: It cannot be stressed enough, that a successful pylon model is one where the complete power-plant and model are correctly matched with themselves and the weather. The dominant factor in engine performance is heat (see 2 stroke theory).

For prop selection it is a compromise between high acceleration (high diameter or area) Vs straight line speed (high pitch). Often a low pitch prop will give faster race times (than high pitch) due to its faster turning / cornering ability. For sports models, wind is a dominant factor. The 8.5 x 7 may be best in calm and 10 x 6SP the best in wind, but less successful when roles are reversed.

Bolly Props are especially suited to competition 'Old Timer' events. Where the rules limit the power plant (as in OT) the biggest advantage is in the propeller.

Despite selling large quantities of props to old timer enthusiasts, very little information is at hand to specific applications. The 13 x 6 has proven very successful as have the 14 x 6, 12 x 6, 11 x 6 and 9.5 x 4.5 in other engine sizes. These 5 sizes are efficient narrow bladed propellers suited to 'climbing' type events.

For most O.T events, a fine pitch prop is generally best, especially for duration. As it so happens the props used by the modern F2B (c/l stunt) model also suit.

To meet these 2 demands the 12 x 4 (narrow), and the broader blade props, the 12.25 x 4.25, 12.5 x 5.5 and 11.75 x 4.25 have been introduced to the Bolly range.

We now have the newer updates to the above designs ... 12.6 x 3.8, 12.2 x 4.2, 11.8 x 3.8 and 11.25 x 4.

Bolly Props were originally produced for C/L only, and therefore we cater for most sizes and events.

For .051(mouse racing), the 5 x 5 or 5.5 x 4 have held many records.

Goodyear (Scale Racing) is a variable world wide (.15 or .21).

For .15 glow use, the G series, ie, G3, G2, G22, G23 (New) are all good as are some of the QM props, the 7 x 5.5 and QM4 (New). For .21, some of the large QM or smaller TR props should work.

Team race (FAI) has seen many of our old 1970's designs deleted to the X-List, and many new choices. The TR80 / 5 series are all developments of a similar style prop, all are good, it's a matter of selecting the correct version for your set-up.

The 'odd-ball' TR events, ie, 1/2A and B will often find a suitable prop amongst the TR or FAI pylon props. For 1/2A or Mini Goodyear the new TR84 should be suitable due to its low blade area. Some 1/2A pylon props may be of use in smaller classes.

Four (4) props are made for FAI speed, all are proven performers and have held national records at one time or another.

Newest is the 6.4 x 6.2 SB. This prop has recently been used to rewrite all Australian records.

A fool proof starting set-up is an Irvine or Rossi, etc, and a 6 x 6 prop.

The 6.2 x 5.7 SB, 6.4 x 6.2 SB and 6.2 x 5.4 SB are square hub single blades suited to competition work. These props can use a specially machined counterweight spinner to suit the square prop hub

By far the biggest success story of Bolly Props is the impact they have had on C/L Stunt. In many parts of the world, Bolly's dominate the top results , top 7 or 8 in 10 is not unusual. Bolly Props have been used to win at least two C/L World Champs and countless Walker Cups (USA Nats).

There appears to be three distinct 'set-ups', dependent on how the pattern is flown. In areas where an 'open' schedule is allowed, big prop loads dominate, as opposed to the 45 degree rule being observed on manoeuvre heights. The third set-up is the tuned pipe.

As with all models, the higher the diameter the more ‘pull’ , especially in vertical climbs etc. With C/L aerobatic models considerable attention must be made to forces of ‘gyroscopic precession’. See the ‘Propellers - Theory’ section of the book.

Whilst 2B props may give better vertical performance, the 3 blade prop will deliver a much smoother, more consistent performance - due to wind up suppression and lessened gyroscopic forces. For higher wind use, the 4 blade props are especially good at limiting 'wind-up'. High pitch props suffer more than low pitch props with the windy ‘wind up’ factor. The downside of low pitch props (unless being used at higher rpm ... =... pipe) is that they can lack ‘bite’ and authority. As with all things it is a compromise.

There has been much said of late about using undercambered airfoil sections on Stunt props. In our experience this is of limited advantage, and only then on large chord props. As Bolly props are of a high aspect ratio blade shape (because it is more efficient), we do not use an undercambered airfoil.

For 1996/7 we have several new props, the 12 x 4.25 3B, 12.6 x 3.8, 12.2 x 4.2, 12 x 6W (nya), 11.8 x 3.8 and 11.25 x 4. Add these to the existing range and it is a big list to choose from.

STD .60 12 x 6, 12 x 6 4B, 12.5 x 6.5 3B, 11 x 7 4B, 13 x 6, 12 x 6.5N 3B

STD .46 12.25 x 4.25, 11.25 x 6.5 3B, 12 x 6W, 12 x 6, 10.5 x 6.25 3B, 11.5 x 6.5

Piped 50/60 12.6 x 3.8, 12.25 x 4.25, 12 x 4.25 3B

Piped 40/45 11.8 x 3.8, 11.75 x 4.25, 11.25 x 4

For electric's use, 3 prop sizes are made in the folding range. For pylon type racing several fixed blade props are often used.

For F3E the 13 x 7 EFP has been often used, and is suitable for considerable thinning.

The 13 x 7 EFP is also used in 'sports' applications - especially gear driven '540' motors.

For direct driven sports gliders (540 + 6 cell) without any doubt the best props is the Bolly 7 x 5.5.

The 9 x 4.5 and 10.25 x 4.5 are used with medium size 7 cell set-ups.

Whilst we do not make 'state of the art' free flight props, two Bolly sizes are very popular and often perform better than the 'fancy' props of the day.

7 x 3 (7.1 x 3.1) for FAI or similar at the ‘base’ level model.

9.5 x 4.5 this prop has won numerous National Championships in Open Power.

For the high rpm uses of free flight, it is best to use carbon fibre propellers.